This invention relates to a resectoscope apparatus for resecting and coagulating tissues within a body cavity.
Recently, there is extensively utilized an endoscope apparatus whereby internal organs within a body cavity can be observed by inserting an elongate insertable part into the body cavity or various therapeutic treatments can be made, as required, by using treating instruments inserted through a treating instrument channel.
As the above mentioned endoscope apparatus, there is a high frequency endoscope apparatus for resecting a prostate, uterus interior, ureter interior or renal pelvis interior. As such a high frequency endoscope apparatus, there is a resectoscope apparatus whereby treatment for the resection of a prostate can be made by inserting the insertable part into the bladder through the urethra and passing a high frequency electric current through a resecting electrode as shown, for example, in the publication of a Japanese Utility Model Application No. 149616/1985.
Generally, a resectoscope apparatus comprises a hollow sheath to be inserted into a body cavity, an operating part having a slider removably fitted to the rear end side of this sheath and an observing scope (optical sighting tube) removably fitted from the rear end side of this operating part. An electrode can project out of and retract into the rear end side of this operating part. The electrode is made like a loop and is branched into two branches at the tip for the resection of tissues within a body cavity. The operating part is provided with a guide tube made of a metal in order to insert the scope. The guide tube projects forward from the sheath connecting part of the operating part, and is inserted into the sheath and provided on the outer periphery rearward from the sheath connecting part with the above mentioned slider so as to be slidable forward and rearward. An electrode inserting tube, inserting and guiding the above mentioned electrode, is provided in parallel with the guide tube. The electrode inserted through this electrode inserting tube is inserted further into an electrode inserting hole of the above mentioned slider and is fixed to an electric contact within the slider. When the electrode is in contact with an affected part and the slider is moved forward and rearward while a high frequency electric current flows, with the forward and rearward movements of the electrode, the affected part will be able to be resected or coagulated.
Since the sheath is inserted into the body cavity, in order to reduce the invasion on the body cavity side, the outside diameter of the sheath must be made as small as possible.
On the other hand, since the optical sighting tube for observing the affected part must also be inserted into the sheath inserting part, in order to observe performance, the larger the optical sighting tube diameter, the better. Since an irrigating liquid is fed into the body cavity through the sheath inserting part as a tube path, in order to secure a clean visual field, sufficient liquid must be input and a space as large as possible must be prepared for the irrigating liquid.
Under such circumstances, the outside diameter of the electrode inserted into the sheath is also restricted. The insulating coating of the electrode can not be made thick enough and, in case a high frequency current is activated, the insulating coating will often be destroyed.
If the insulating coating of the electrode is destroyed, in the conventional resectoscope apparatus, electric current will leak to the patient and the operator from the conductive material coming out to the shielding part of the resectoscope apparatus through the conductive material such as a metal near the destroyed insulating part.
Even if the insulation is not destroyed, since a high frequency current (usually of several 100 KH.sub.z) is used, even if the coating member of the electrode inserted through the sheath is sufficiently insulated from direct current, when the disinfection with chemicals is repeated, the insulation from high frequencies will be greatly reduced. Thus, when the insulation of the sheath from the electrode through which the high frequency current flows, is reduced, the high frequency current will flow to the inside wall of the body cavity of the patient into which the sheath is inserted and no sufficient safety will be secured.
Also, in case the resecting electrode is inserted through the sheath, if the electrode is bent, it may contact the inside wall surface of the sheath. In such a case, even if the insulation from the direct current is kept by the coating material, the high frequency current may leak out to the sheath side through a minute capacity.
For the purpose of preventing the electric current from leaking out to the patient and operator, there are suggested by the present applicant, for example, a Japanese Patent Application No. 23186/1988 wherein the guide tube of the operating part is formed of an insulating material or the connecting part of the operating part is formed of an insulating material and a Japanese Patent Application No. 292919/1985 wherein at least the inside diameter or outside diameter of the inserted part of the sheath jacket tube is provided with a ceramic layer.
However, in the above mentioned art, somewhere in the sheath and operating part of the resectoscope, conductive material such as a metal has been used in a component part which is likely to contact the patient and operator.
Therefore, leaking current by the minute high frequency capacity, by the reduction of the high frequency insulation of the insulating coating part of the electrode or by the insulation destruction of the insulating coating part of the electrode as is described above can never be made to reach the patient and operator. A further problem is that, even if the respective parts are separately partly made of an insulating material, if conductive material as a metal is used in a part, the leaking current will concentrate on this conductive material by avoiding the other insulating materials and, if the patient or operator touches the conductive material, the current density will become larger, a burn or shock will likely be generated and it will be rather dangerous.